Burner control apparatus



April 1963 w. A. REICHOW 3,086,583

BURNER CONTROL APPARATUS Filed on. 12, 1959 FLAME o DETECIOR INVENTOR.

WILLIAM A. REICHOW ATTORNEY United States Patent 3,086,583 BURNER CONTROL APPARATUS William A. Reichow, Kansas City, Mo., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Filed Oct. 12, 1959, Ser. No. 845,811 5 Claims. (Cl. 158125) The present invention is concerned with an improved burner control apparatus and particularly with a burner control apparatus having means to detect a leaking fuel valve which would allow a dangerous amount of unburned fuel to accumulate in the vicinity of the fuel burner unit which is being controlled.

-A fuel burner unit normally consists of a main fuel burner which is connected to a fuel supply conduit having a normally closed valve. The control apparatus associated with the fuel burner unit is effective to cause this valve to open and admit fuel to the fuel burner unit upon a call for operation of the fuel burner unit. The fuel which flows from the main burner is then ignited by manual means, or may be automatically ignited by means of a pilot burner or ignition means such as spark ignition. Once there is a call for operation of the fuel burner unit, it is necessary to provide safety cutout means, commonly known as a safety switch, which in conjunction with a flame detector is effective to allow a time period during which flame must be established. It flame is not estab lished during this time period, the safety switch is effective to de-energize the components of the fuel burner unit and the apparatus, including the fuel burner unit, is placed in a safety lockout or safety shutdown condition such that it is necessary to first correct the fault which caused the fuel to fail to ignite and to secondly reset the safety switch before a further attempt can be made to establish flame at the fuel burner.

During the standby condition of the apparatus, that is during the condition in which there is no call for operation of the fuel burner unit, it is possible for the fuel valve either to stick in an open position or to fail to completely close so that fuel continues to leak into the fuel burner. This fuel continues to accumulate until such time as there is a further call for operation of the fuel burner. At this time, the ignition means is energized and the accumulated fuel is ignited, often with disastrous results.

The present invention is directed to an improved burner control apparatus which not only provides adequate safe monitoring of the operation of the fuel burner unit during a period in which there is a call for operation of this unit (the running period), but also provides a means which detects the presence of a leaking gas valve during the standby period.

Specifically, the present invention provides a flame detector which functions to insure that flame is at all time present during a call for operation of the fuel burner unit. If a flame fails to be established, or it once established the flame becomes extinguished, then the flame detector, in conjunction with a safety cutout means, is effective to de-energize the fuel burner unit and place the unit in a safety lockout condition. Furthermore, the apparatus of the present invention utilizes this same flame detector, in

conjunction with further means which samples the air in the vicinity of the fuel burner, to function during the standby period such that in the event the gas valve is open or slightly open during this standby period, combustion is established and the flame detector senses this combustion to place the apparatus in a safety lockout condition.

In this manner, a single flame detector functions not only during the running period, but also during the standby period of the fuel burner unit to insure the optimum ice 2 in safety. Specifically, this is provided by utilizing a valve which is open during the standby period and allows air in the vicinity of the fuel burner to pass over a second igniter. This open valve is closed during the operating period of the fuel burner unit. However, during the standby period, the valve is open and a fan is utilized to draw air from the vicinity of the fuel burner unit over the second igniter. If the valve fails to close, unburned fuel is drawn over the the second igniter and combustion is established. The flame detector now senses this combustion and the safety lockout means is energized to cause the apparatus to go out on safety lockout and thereby insure that no subsequent attempt may 'be made to establish flame at the fuel burner unit, thereby eliminating the possibility of an explosion upon such a subsequent attempt. Furthermore, it is possible with the present apparatus to provide further indicator means, for example an alarm, which is immediately energized in the event that combustion is detected during the standby period of the fuel burner unit.

The present invention will be apparent to those skilled in the art upon reference to the following specification, claims, and drawing, of which the single FIGURE is a schematic representation of a preferred embodiment of the present invention.

Referring now to the drawing, the reference numeral 10' designates generally a fuel burner unit having a main fuel burner 11 which is connected to a supply of fuel by means of a fuel supply conduit 12 having a normally closed valve 13 disposed therein. The reference numeral 14 designates a pilot burner which is connected to the fuel supply conduit 12 by means of a further conduit 15, which conduit includes a normally closed valve 16. The reference numeral 17 designates an ignition electrode which is connected to an ignition transformer 18. Ignition electrode 17 is disposed in igniting relation to the pilot burner 14 and the combination of pilot burner 14 and ignition electrode 17 can be designated as an ignition means for the main burner 11.

The reference numeral 19 desigantes generally a fuel leak detecting means which, as will be apparent, is operative in conjunction with a flame detector, to sense the presence of a fuel leak, for example at valve 13. The means 19 includes a normally open valve 20, a fan 21, an ignition chamber 22, and a nozzle or burner tip 23. Valve 20 is open when in a de-energized state. In this manner, valve 20 differs from valves 13 and 16, these latter valves being closed when in a de-energized state.

When the valve 20 is open, that is when the valve is de-energized, fan 21 is effective to draw fluid from that portion of the fuel supply conduit 12 which lies between valve 13 and burner 11 up through valve 20 and through fan 21. This fluid is passed over an igniter 24. If valve 13 is in an open or a partially open condition at this time (as it should not be) then igniter 24 is effective to ignite the fluid which is drawn into chamber 22 by fan 21 and combustion is established at nozzle 23.

Combustion detecting means is provided to detect both the presence of combustion at burners 11 and 14 as well as combustion which may be present at nozzle 23. This means is identified generally by means of the reference numeral 25. Specifically, the means 25 may consist of an electronic flame detector whose operating voltage is received from a pair of alternating current power line conductors 26 and 27 which are connected to a source of alternating voltage, not shown. The input of flame detector 25 is connected to a condition sensor 28 while the output of this flame detector includes a flame relay 29.

Condition sensor 2.8 is shown as a Geiger tube type condition sensor in which a pair of electrodes 30 and 31 are disposed in an ionizable gaseous medium. It is within the teachings of the present invention to provide other types of condition sensors, for example photovoltaic or photoemissive cells, all of which fall within the generic term of a condition sensor and all of which may be used to sense the presence of combustion at the burners 11 and 14 and at the nozzle 23.

Flame relay 29 is provided with an electrically energizable actuating winding 32 as well as with normally closed switches 33- and 34 and normally open switches 35 and 36. Flame detector 25 is shown in the condition wherein the condition sensor 28 does not sense the presence of combustion at the fuel burner unit 10. In this condition, relay winding 32 is de-energized and therefore the switches assume the position shown in the drawing. Upon condition sensor 28 being subjected to the presence of flame at either the burners 11 or 14 or at the nozzle 23, condition sensor 28 is effective to control flame detector 25 and cause relay 29 to be energized. When this occurs, switches 33 and 34 open and switches 35 and 36 close.

Overall control of the fuel burner unit is accomplished by means responsive to the need for operation of the fuel bumer unit, this means being in the form of a thermostat identified by reference numeral 37. This thermostat is responsive to the temperature of the space heated by fuel burner unit 10 and upon the temperature being reduced to a given value, thermostat 37 closes its normally open switch and a main burner control relay 39 is energized to energize the fuel burner unit 10, as will be explained. Main burner control relay 39 is provided with an electrically energizable winding 40, a normally closed switch 41, and normally open switches 42 and 43.

Operating voltage for the control network including relay 39 is derived from a transformer 44 having its primary winding connected to the power line conductors 26 and 27 and having its secondary winding connected in circuit with thermostat 37, relay 39, and a safety lockout means in the form of a safety switch 45. Safety switch 45 is provided with a normally closed switch 46, a bimetal control member 47, and an electrically energizable heater 48. The safety cutout means 45 is of conventional construction and functions such that a time period after energization of heater 48, bimetal 47 is heated sufficiently such that its upper end moves to the left and releases switch 46 so that this switch opens. Switch 46 may reset to its closed condition by means of a reset button 49.

Referring now to the operation of the apparatus, the condition of the apparatus as shown in the single FIG- URE is the standby condition. In this condition, thermostat 37 is in a condition indicating that there is no need for operation of the fuel burner unit 10. As a result, burner control relay 39 is de-energized and valves 13-, 16 and 20, as well as ignition transformer 18 are also deenergized. In this condition, there should be no unburned fuel present Within the section of the fuel conduit '12 between valve 13 and main fuel burner 11. Since valve 20 is a normally open valve, this valve, when deenergized, is in an open condition. Fan 21 and igniter 24 are directly connected to the power line conductors 26 and 27 are therefore both energized. Fan 21 is effective to cause the atmosphere within the above mentioned portion of fuel conduit '12 to pass through the open valve 20 and through fan 21 into chamber 22 where this atmosphere is subjected to igniter 24 and passes out of nozzle 23. Normally, this atmosphere does not contain unburned fuel. Therefore, no combustion is established at the nozzle 23. Therefore, flame detector 25 and condition sensor 28 do not sense the presence of combustion and flame relay 29 remains in its de-energized condition, as shown.

Assume now that there is a call for operation of the fuel burner unit. This is evidenced by thermostat 37 closing its switch to establish an initial energizing circuit for winding of main burner control relay 39. This initial energizing circuit can be traced from the upper terminal of the secondary winding of transformer 44 through conductor 50, thermostat 37, relay winding 40, switch 46, conductors 51 and 52, flame relay switch 33, and the actuating heater 48 of safety switch 45 to the lower terminal of this secondary winding. From this circuit it can be seen that energization of relay winding 40 takes place only if first, safety switch 45 is in a condition wherein its switch 46 is closed, and second, flame relay 29 is in a de-energized condition such that its switch 33 is closed. As will be evident later, this type of circuit is utilized to insure that the main burner control winding 40 may not be energized in the event that fuel leak detector 19 has detected the presence of unburned fuel in the vicinity of the main burner 11 during the standby period.

Energization of relay 39 causes switch 41 to open and switches 42 and 43 to close. Switch 42 is connected to a tap 54 on the [transformer secondary winding and this switch is effective to complete running energizing circuits for the burner control relay 39 as well as a maintaining energizing circuit for the safety switch heater 48, this latter circuit being under the control of flame detector 25.

Considering first the running energizing circuit for main burner control relay 29, this circuit can be traced from the upper terminal of the secondary winding through conductor 50, thermostat 37, winding 40, switch 46, conductors 51 and 55, switch 42, and conductor 56 to the transformer tap 54. The maintaining energizing circuit for safety switch heater 48 can be traced from the lower terminal of the transformer secondary winding through heater 48, flame relay switch 33, conductors 52 and 55, switch 42, and conductor 56 to transformer tap 54. From these above traced circuits it can be seen that relay winding 40 is maintained energized so long as thermostat 37 remains in a condition indicating a need for operation of the fuel burner unit 10 and so long as the switch 46 remains in a closed condition. The heater 48 of safety switch 45 remains in an energized condition so long as relay 39 remains energized and so long as the flame relay 29 remains de-energized, that is remains in a condition indicating the absence of flame in the fuel burner unit 10. This latter circuit provides a time period during which a flame may be established at the fuel burner unit 10. If a flame is not established during this time period, bimetal 47 warps to the left so that switch 46 opens. The opening of this switch causes the main burner control relay 39 to be de-energized and as a result the apparatus is placed in a safety lockout condition.

Normally however a flame is established at fuel burner unit 10. The energizing circuit for the components of fuel burner unit 10 can be seen by tracing a circuit from power line conductor 27 through conductor 57, switch 43, conductors 58, 59 and 60 to the pilot valve 16 and then to the other power line conductor 26. The energizing circuit for ignition transformer 18 can be seen by tracing a circuit from the above mentioned conductor 58 through conductor 62, flame relay switch 34, conductor 63 and ignition transformer 18 to the other power line conductor 26. As a result of these two circuits, pilot valve 16 opens and ignition transformer 18 is energized to thereby normally establish a pilot flame at pilot burner 14. Furthermore, at this time the normally open valve 20 associated with fuel leak detecting means 19 is energized by means of a circuit which can be traced from power line conductor 27 through conductor 57, switch 43, condoctors 58, 59 and 72 to valve 20 and from valve 20 to the other power line conductor 26. With the energization of valve 20, this valve closes and fan 21 is no longer effective to draw fluid from conduit 12 through chamber 22. This is of course necessary since during a period of call for operation of the fuel burner unit 10, unburned fuel is of necessity present in the vicinity of the fuel burner "11 and particularly in supply conduit 12 for this fuel burner. Therefore, it is necessary to render fuel leak detecting means 19 inoperative at this time.

As mentioned, a flame is normally now established at pilot burner '14 and this flame is detected by condition sensor 28. As a result, flame relay 29 is energized and its switches 33 and 34 open while its switches 35 and 36 close. The opening of switch 33 opens the above traced maintaining circuit for heater 48 of safety switch 45 and as a result this safety switch is rendered inoperative, this being accomplished as a result of the fact that flame is established at the pilot burner 14.

The opening of switch 34 de-energizes ignition transformer 18, its spark no longer being necessary since a flame is established at pilot burner 14. The closing of switch 36 completes an energizing circuit for the main fuel valve 13. This energizing circuit can be traced from power line conductor 27 through conductor 57, switch 43-, conductors 58 and 62, switch 36, conductor 63 and valve 13 to the other power line conductor 26. As a result, valve 13 opens and fuel is admitted to the main fuel burner 11 where it is ignited by the igniting means, that is the pilot flame present at pilot burner 14.

The closing of switch 35 by flame relay 29 has no effect at this time. However, this circuit is effective, as will be explained, in the event that a leaking fuel condition is detected during the standby period.

The apparatus at this time is in a running condition wherein valves 13, 16 and 20 are energized, ignition transformer 18 is de-energized, fuel leak detecting means '19 is inoperative since valve 20 is closed, and relays 29 and 39 are energized. This condition is maintained so long as there is a continued need for operation of the fuel burner unit 10. At the end of a period of such a need, thermostat 37 opens its switch and therefore de-energizes relay 39 to cause its switches to revert to the position shown in the singe figure. The opening of switch 43 de-energizes the valves 13 and 16 of the fuel burner unit and also de-energizes the normally open valve 20, thereby causing this valve to open. The opening of valve 20- renders the fuel leak detecting means 19 again operative and so long as relay 39 remains de-energized, as it does when there is no call for operation of the fuel burner unit 10, the means 19 is continuously operative to monitor the presence or absence of unburned fuel in the vicinity of the main fuel burner 11.

Specifically, with valve 20 open, fan 21 draws the atmosphere in conduit 12 over igniter 24 where any unburned fuel is ignited.

For purpose of explanation, let us assume that valve '13 fails to completely close and a partial flow of unburned fuel is allowed to pass to burner 11 during the standby condition of the apparatus, that is the condition shown in the figure. This unburned fuel, or at least a portion of this fuel, is drawn through valve 20 and into chamber 22 where it is ignited. A flame is therefore established at nozzle 23. This flame is detected by condition sensor 28 in much the same manner as condition sensor 28 detects the presence of flame at the pilot burner 14 or the main fuel burner 11. As a result, flame relay 29 is energized and its switches 33 and 34 open whereas its switches 35 and 36 close. The opening of switch 33 breaks the initial energizing circuit for the main burner control relay 39, with the result that in the event there is now a call for operation of the fuel burner unit 10, thermostat 37 is ineffective to energize relay 39 and therefore switch 43, which switch is connected in controlling relation to the fuel burner unit 10, remains in an open condition.

Furthermore, the opening of switch 34 opens the circuit to ignition transformer and therefore insures that this ignition transformer may 'not be energized. It will be immediately recognized that the energization of ignition transformer 18 at this time may possibly ignite a large quantity of accumulated unburned fuel in the vicinity of the main fuel burner 11 and thereby cause a disastrous explosion.

The closing of switch 35 completes a circuit to energize the heater 48 of safety cutout means 45. This circuit can be traced from the lower terminal of the transformer secondary winding through heater 48, switch 35, conductor 64, switch 41, and conductor 56 to the tap 54 of the transformer secondary winding. It will be remembered from the above explanation that relay winding 39 may not be energized at this time due to the fact that flame relay switch 33 is in an open condition. Therefore, switch 41 must remain in a closed condition. So long as flame detector 25 detects the presence of flame at nozzle 23, its switch 35 likewise remains in a closed condition and therefore safety switch 45 is caused to go to a safety lockout condition wherein switch 46 is opened. As a result, the apparatus is placed in a safety lockout condition wherein the initial energizing circuit for the main burner control relay 59 is opened at switch 46. As is well known, the safety lockout means 45 may include a normally open switch, not shown, which is closed at the same time as switch 46 is opened. The closing of this further switch may be utilized to control various alarm means to call attention to the fact that the control apparatus has detected a faulty condition at the fuel burner unit '10.

A further inherent feature of the apparatus resides in the fact that it is possible with most flame detectors for components of these flame detectors to fail in what may be called an unsafe failure. An unsafe failure is defined as a failure in which flame relay 29 becomes energized to indicate the presence of flame when in fact a flame is actually not present. Such a failure of the flame detector 25 acts in the same manner as condition sensor 28 detecting the presence of flame at nozzle 23 and also causes the safety switch 25 to assume a safety lockout condition.

From the above it can be seen that I have provided an improved burner control apparatus which controls and monitors the operation of a fuel burner unit 10 and in which a gas leak detecting means 19 is provided to operate in conjunction with flame detector 25-28 and insures that the apparatus provides safe operation of the fuel burner unit 10 at all times, including the condition wherein valve 13 develops a leak or sticks in the open condition. The apparatus of the present invention accomplishes this by the use of a single flame detector and safety switch which operate both during the running and during the standby conditions of the fuel burner unit and therefore safely monitor the conditions at the fuel burner unit at all times. Futhermore, this is accomplished with a minimum of auxiliary equipment.

Other modifications of the present invention will be apparent to those skilled in the art and it is therefore intended that the scope of the present invention be limited solely by the scope of the appended claims.

I claim as my invention:

1. Burner control apparatus for use with a fuel burner unit having a normally closed valve controlling the flow of fuel to a fuel burner and having igniting means asso ciated with the fuel burner to ignite the fuel thereat, comprising; a controller responsive to the need for operation of the fuel burner unit, means including said controller adapted to energize the igniting means upon such a need and to then open the valve upon proper operation of the ignition means, a flame detector adapted to monitor the proper establishment of combustion at the fuel burner, means including said flame detector for detecting a fuel leak at the normally closed valve during a standby period in which said controller is not calling for operation of the fuel burner unit, safety cutout means adapted to be placed in controlling relation to the fuel burner unit, and means controlled by said controller and said flame detector to actuate said safety cutout means in the event of failure to properly establish combustion or in the event a fuel leak occurs.

2. Burner control apparatus for use with a fuel burner unit having a normally closed fuel valve, comprising; means responsive to the need for operation of the fuel burner unit, ignition means, means controlled by said means responsive to the need for operation of the fuel burner unit to control said ignition means to establish an ignition condition at the fuel burner unit and to then open the fuel valve, time delayed safety cut-ofi means having a timing period and adapted to be placed into operation upon the need for operation of the fuel burner unit, means placing said time delayed safety cut-off means in controlling relation to the fuel burner unit, a combustion detector adapted to sense the presence or absence of combustion at the fuel burner unit, means placing said combustion detector in controlling relation to said safety cut-off means to render the same inoperative upon establishment of combustion at the fuel burner unit within said timing period, unburned fuel detecting means including said combustion detector and rendered operative only during the period in which there is not a need for operation of the fuel burner unit to detect the presence of unburned fuel at the fuel burner unit, and further means adapted to place said safety cut-off means into operation in the event that unburned fuel is detected at the fuel burner unit during said last named period.

3. Burner control apparatus for use with a fuel burner unit having a fuel valve operative to control the flow of fuel to the fuel burner unit, and having ignition means to ignite the fuel at the fuel burner unit, comprising; control means responsive to the need for operation of the fuel burner unit, means including said control means operative upon such a need to render the ignition means operative and to then open the fuel valve such that a flame is normally established at the fuel burner unit, a flame detector associated with the fuel burner unit and eifective to monitor the flame condition in the vicinity of the fuel burner unit, safety cut-out means, means placing said safety cut-out means in controlling relation to the fuel burner unit, means controlled by said flame detector and effective to render said safety cut-out means operative in the event that a proper flame condition does not exist at the fuel burner unit during periods of a need for operation of the fuel burner unit, and fuel leak detecting means including said flame detector and controlled by said control means to be operative during periods when there is not a need for operation of the fuel burner unit to render said safety cut-out means operative in the event that a fuel leak is detected during the period in which the fuel valve is not operative to admit fuel to the fuel burner unit.

4. In a burner control apparatus for use with a fuel burner unit having a normally closed fuel valve, a flame detector including a flame relay and including flame sensing means associated with the fuel burner unit to monitor the presence or absence of flame in the vicinity of the fuel burner unit, electrically energizable safety cutout means including an actuator, means connecting said safety cutout means in controlling relation to the fuel burner unit to render the same inoperative after a time period of energization of said safety cutout means actuator, switch means controlled by said flame relay effective to alter the circuit of said safety cutout actuator and thereby de-energize said actuator upon a flame being sensed at the fuel burner unit, fuel leak detecting means including igniting means associated with the fuel burner unit, control means effective to render said fuel leak detecting means operative only during the periods in which there is no operation of the fuel burner unit and effective to establish a condition of combustion during those periods in the event that a fuel leak exists during those periods, while the fuel valve is normally closed and is normally not operative to admit fuel to the fuel burner unit, and further circuit means controlled by said flame relay and effective upon said flame detector detecting the presence of such combustion to energize the actuator of said safety cutouts means.

5. A burner control system comprising; a main burner having a normally closed main valve disposed in a fuel supply conduit upstream of the main burner, first igniting means associated in igniting relation with the main burner to ignite the fuel flowing therefrom and including a normally closed pilot valve and a pilot burner, second igniting means, a further fuel conduit connected to said fuel supply conduit between the main valve and the main burner and including a normally open valve to allow the atmosphere existing between said normally closed main valve and the main burner to pass to said second igniting means, control means responsive to the need for operation of the burners and operative upon such a need to open said normally closed pilot valve to render said first igniting means operative such that fuel flows to the pilot burner and is ignited thereat, further means controlled by said control means upon a need for operation of the burners to close said normally open valve and thereby prevent fuel from being drawn to said second igniting means, a flame detector associated with the burners and effective to monitor the flame condition in the vicinity of the burners, safety cutout means controlled by said flame detector and by said control means and effective upon a failure of said flame detector to detect the presence of flame at the pilot burner a time period after the opening of said normally closed pilot valve to render the normally closed pilot valve inoperative, and further means including said flame detector controlling said safety cutout means to render said safety cutout means operative in the event that said flame detector senses the presence of combustion caused by said second igniting means during the period in which there is not a call for operation of the burners, said combustion being indicative of a fuel leak at said normally closed main valve.

References Cited in the file of this patent UNITED STATES PATENTS 2,532,214 Willenborg Nov. 28, 1950 2,538,222 Wilson Jan. 16, 1951 2,585,882 Weissman et al. Feb. 12, 1952 2,800,176 Warrison July 23, 1957 

1. BURNER CONTROL APPARATUS FOR USE WITH A FUEL BURNER UNIT HAVING A NORMALLY CLOSED VALVE CONTROLLING THE FLOW OF FUEL TO A FUEL BURNER AND HAVING IGNITING MEANS ASSOCIATED WITH THE FUEL BURNER TO IGNITE THE FUEL THEREAT, COMPRISING; A CONTROLLER RESPONSIVE TO THE NEED FOR OPERATION OF THE FUEL BURNER UNIT, MEANS INCLUDING SAID CONTROLLER ADAPTED TO ENERGIZE THE IGNITING MEANS UPON SUCH A NEED AND TO THEN OPEN THE VALVE UPON PROPER OPERATION OF THE IGNITION MEANS, A FLAME DETECTOR ADAPTED TO MONITOR THE PROPER ESTABLISHMENT OF COMBUSTION AT THE FUEL BURNER, MEANS INCLUDING SAID FLAME DETECTOR FOR DETECTING A FUEL LEAK AT THE NORMALLY CLOSED VALVE DURING A STANDBY PERIOD IN WHICH SAID CONTROLLER IS NOT CALLING FOR OPERATION OF THE FUEL BURNER UNIT, SAFETY CUTOUT MEANS ADAPTED TO BE PLACED IN CONTROLLING RELATION TO THE FUEL BURNER UNIT, 